Apparatus for crystallizing liquids



Jan. 1s, 1927, 1,615,151

G. T. WALKER AYPARATUS FOR CRYSTALLIZING LIQUIDS Filed Nov. 28, 1921 2 SheetswSheol N Q@ mw mm,

1 I 1,615 151 Jan. 18, 1927. G' T. WALKER APPARATUS FOR CRYSTALLIZING LIQUIDS Filed NOV. 28, 192] Sheets-$11661 2 /7706/7/0/ GfoRqf 7i h//YL KEA Patented 18, 192?.D

UNITED PTENT OFFICE.

G-ERGE T. WALKER, OIE' MLWAUKEE, WISCONSIN.`

APPARATUS FOR CRYSTALLIZING- LIQUIDS.

`Application filed November 2S, w21. Serial No. 5185341.

generally, they united in large masses which adhered very firmly to the walls and bottom of the tank. A. great deal of manual labor. was required for the removal of the product, cooling was .slow and dependent on'the temperature of the air. This very simple process when applied on a large scale resulted in a high labor cost, and a heavy investment for tanks and buildings. The product had to be ground or pulverized if large lumps were not desirable and it was subject to various forms of contamination during handling. llt was found that the process could be improved by stirring' the solution from time to time and the use of a jacketed tank which was water-cooled would hasten the rate of cooling provided some means was rovided to keep the cooling surface clear from the layer of crystals which tended to form on it.

In the effort to apply the above principles three styles `of mechanical crystallizers were produced: The so-called Buffalo crystallizer which was simply a large waterjacketed saucer with a vertical shaft bearin two plows which scraped the bottom and si es as the revolved. Another arrangement comprised a. tank of approximatelyV equal depth and diameter provided with coils for the cooling medium and a rapidly revolving propeller or stirrer which kept the surfaces of the coils relatively clean because of the scouring action of the rapidly whirling liquid and crystals. The third commercial device was the Bach crystallizer which was a large horiaontal jacketed cylinder provided with slowly moving Scrapers to remove the crystals from the inner surface of the cylinder.

While each of these types has been used considerably, they all required considerable attention and were very wasteful of water if it were necessary to cool the liquid to a temperature near that of the cooling water.

Furthermore, in these devices the wastage'of coolmg water was excessive ecause during the latter stages of cooling each batch, the

cooling water running from the crystallizer was practically as cold as when it entered.

lin many processes, the nal temperature of the cooled liquid must be closely controlled in order to avoid contamination of oo the product by crystallization of some form i of impurity whichA would separate when the temperature was carried too low. To avoid this, when using batch machines which produced only a small tonnage per unit, it was t5 necessary to exercise most careful control of the cooling. Y

rElie main object of the present invention is to provide a machine for the above purposes which is economical in the use of cooling watersince the cold water cools the cold liquid and as it progresses through the machine is continually cooling warmer liquid; requires only a small amount of power; re-

quires practically no labor or attention;l is

self-discharging; occupies a minimum -of door space; is cheaply constructed; can be adjusted to produce crystals of uniform size; is readily accessible at all times and at all points; can be easily regulated to produce so a continuous discharge at a constant temperature and produces practically pure crystals from an impure liquid which are much less fragile than those produced by other apparatus or methods, and therefore, pro

duce less dust when handled.

Still another object of this invention re sides in the novel process of producing crystals of large and more uniform size.

These and other objects will in part be obvious and will in part be hereinafter more fully disclosed.

The one form of apparatus disclosed in this application comprises Vbroadly a chamber to receive `a, heated liquid and a novel water jacket through which water is run to cool the liquid in the chamber. Preferably, the heated liquid is introduced within the chamber at one end thereof and is slowly impelled toward its outlet adjacent the other end thereof, while the cooling water travels through the water jacket as a counter-current, that is, the cool water is introduced within the water jacket adjacent the outlet of the heatedliquid from the chamber, so lthat the discharging liquid is subject to the influence of the entrant relatively cool water.

The apparatus shown in the accompanying j drawings is that of a present commercie i1 ,man

embodiment, of the invention adapted for employment as a counter-current crystallizer. The heated crystallcidal liquid is introduced within the chamber at one end and discharged at the other end, while the cooling water under suitable head enters the water jacket. adjacent the discharge end of the chamber and has its outlet at the intake end of the chamber. The crystalloidal heated, liquid is slowly moved through the open-topped chamber by either the natural inflow and discharge of the liquid or by means of a suitable impeller such as a modified form of screw Conveyer comprising, as here shown, a rotatable shaft extending through the chamber and having a ribbon thereon which makes less than a vcomplete turn about the working portion of the relatively long shaft. A crystallizer of this present type is preferably about forty feet in length and the shaft is rotated about onel revolution per minute in order that the heated liquid may be exposed-to water of seasonal temperature sufliciently long to precipitate the crystals for subsequent removal.

In the accompanying drawings, there has been discloseda structure designed to carry out the objects of the invention, but it is to be understood that the invention is not confined to the exact features shown, as various chan es may be made within the scope of the c aims which follow.

In the drawings: l

Figure 1 is a longitudinal median sectional view of the apparatus on the lines 1-1 of Figures 4 and 5;

Figure 2 is a plan view of the assembled apparatus;

Figure 3 is a longitudinally sectional View, on the lines 3 3 of Figures 4 and 5; Figure 4 is a cross-sectional view on the line 4--4 of Figure 3;

Figure 5 is a similar view on the line 5--5 of Figure 3; and

Figure 6 is a sectional view of the liquid .p

intake end of theA apparatus.

In this selected embodimentl of thel invention here shown, there is provided a chamber substantially U-shaped in cross-section and thus open along the top. This chamber is preferab the desired form. 'Preferably the apparatus is made up of a pluralit of similar chamber units adapted for assemlily into an elongated apparatus-as used at present the chamber is slightly less than forty feet long. I In Figure "2, there are shown four such chamber units, 11, 12, 13 and 14* in assembled terminally abutting relation. Adjacent units are held together with a water-tight connection by means of complementary angle irons 15 having portions respectively held by rivets 16 to each other and to the terminal portions of the abutting ends of adja y formed of sheet steel shaped to cent chamber units. The semi-cylindrical or U-shape is employed because it is readily accessible at any point and at any stage of the operation. For this reason it is much easier to start it again if failure of power results in a shut-down. These advantages are lacking in the cylindrical machine.

The elongated chamber of the assembled apparatus is provided with an intake connectlon 17 adjacent one end of the chamber by means of which the heated liquid may be introduced within the open-topped chamber and with adischarge connection 18 adjacent the opposite end of the chamber. Means are provided within the chamber to impel the heated liquid. A shaft 19 extends longitudinally through the chamber'and is provided with gland bearings 21 at each end of the chamber, as the shaft, in this embodiment of the apparatus, is long, it is desirable to provide intermediate bearings there# for. Bearings 22 are integrally depended from hangers 23 carried by cross-arms 24 mounted transversely upon the longitudinal edges of the two chamber sides. The hangers are secured to the cross-arms 24 by rivets 25 and the cross-arms are in turn held to the chamber sides by means of the angle plates 26 riveted both to the sides of the chamber and to the terminal portions of the cross-arms as shown in Figures 4 and 5. An elongated or ribbon-like blade is substantially spirally carried by the shaft 19. This blade is preferably not continuous in order that the intermediate shaft bearings 22 may be employed. Hence, the blade is formed of a plurality of complementary sections 27. The blade sections 27 are carried by spokes 29 suitably secured to the shaft at spaced intervals. As is shown in Figure 2, this blade is substantially spirally disposed about the shaft 19 but preferably does not effect a complete turn about the shaft in order that the heated liquid may be sluggishly impelled by the slow rotation of the shaft 19 from any ower source Anot necessary to be shown. The heated liquid may be introduced within the chamber by way of the intake connection 17 indicated at the right end ofl Fi ure 2 and as shown in Figure 6. This en may be termed for sake of clarity, as the front end of the apparatus, while the opposite end having the liquid discharge connection 18, may be termed the rear end. The liquid is very slowly moved by the shaft blade toward the rear end of the machine and, during its motion, the liquid is gradually cooled by water running through the surrounding Water jacket in an opposite direction.

The water jacket is provided with means for causing the current of water to pursue a tortuous course in its transit of the chamber exterior. Similarly to the chamber, the water jacketin is effected by a plurality of units, each icing secured to a chamber Btl Bti

tinit and a pipe connection being provided successively to connect the water jacket units. lEach water jacket unit is formed by a casing 3l comprisin a piece of sheet metal shaped to exten about its supplementary chamber unit in spaced relation thereto. -'lhe two longitudinal edge portions 32 of the casing are 'both inwardly odset and are held tightly against the adjacent outer surface of the chamber unit by means of the depending sections of the riveted angle plates 26. A water-tight closure of the top of the Water jacket is thereby effected. 'llhe ends of the water jacket casings are closed by means of the lll-shaped bars 33, the end portions of the casing extending over the outer faces of the bars and rivets being passed through the casing, bars and chamber units. The cooling water is supplied under sufficient head to the water inlet connection 34 and thus enters the rear unit i 1li and thereafter is successively passed to of these itl-shaped bathe plates 37 is shorter than the other, and these plates are alternately disposedA in spaced relation in each water jacket unit. rlhus, the moving water passes over the shbrt leg of one baffle plate at one side of the chamber unit and must then travel to the other side of the chamber unit to the next short leg, etc. Such balledI course ,of the cooling water causes a more effective and uniform cooling of the chamber and therefore of the heated liquid therein. The jacket as above described, is so constructed that the cooling medium can be distributed in a thin layer in order to obtain a hi h velocity of flow with a relatively' smallr amount of water. High velocity causes an increased heattransmission. The battles also servethe same purpose as they cause the cooling mediumto follow a long route and therefore to travel at a high rate of speed. Transverse baffles are used in preference to longitudinal baffles or partitions in order that the water may be continuously warmed as it passes through theI machine and yet always be cooler than the liquid to be cooled at any point. In the case Vof longitudinal bailes or partition as the water was warmed it would pass alternately from the warm tothe cool end of the crystallizer and therefore will be warmer than the liquid to be cooled at the cool end of the machine unless an unnecessarily large volume of water is used. Such baffling is not based on the true counter-current principle. While the jacket in my machine causes a high velocity of the cooling medium the passages are large and the use of large connections from section to section allow the use of a large volume of water and therefore the use of very long units for large capacity with minimum attendance.

ln the present operation of this apparatus in connection with heated crystalloidal liquid, such liquid is supplied to the chamber by means of the intake connection 17 so that the chamber is filled to the level of the discharge connection 18. The water runs.

from the rear end to the front end through the water jacketing. The shaft 19 is slowly revolved so that the liquid is very gradually moved toward the rear of the chamber while any crystals formed by the cooling of the liquid are likewise moved toward the rear end of the apparatus. The cooled liquid is slowly discharged through the discharge connection 18 carrying with it any crystals which are capable of oating in the liquid whereupon the crystals are subsequently recovered, or the crystals may be precipitated to the bottom of the casing and :slowly kgathered at the rear end throu h action of the impeller whereat they may e recovered from time to time.`

llt will be noted that aspiral of extremely long pitch is used. A. standard spiral of a pitch about equal to the diameter merely pushes the crystals forward without liftlng them so that they will not be discharged unless there is an opening in or nearthe bottom. Such an opening 'would'make it impossible to fill the machine with liquid and therefore only a small portion of the cooling surface would be actually available.

`The long spiral has a lifting effect so that the crystals are constantly and repeatedly lifted and allowed to fall through the liquid. During this process growth occurs so that coarse crystals can be produced although the rate of stirring is relatively rapid. This lifting and rapid4 stirring keeps the cooling surface clean and prevents insulation although there is no contact of metal with metal, which would cause a great increase in the power required and result in -contamination of the crystals bythe i articles of metal removed by such contact. o keep such contact would -also require frequent adjustment and severe wear. This lifting effect also furnishes a means of-discharging the crystals from the machine so that it can be operated continuously. When first filled very few crystals are discharged but they are gradually carried forward by the spiral and the flow of the vliquid which is being constantly introduced at the hot end. In time the density of the mixture of crystals and liquid at the cool end becomes sufficient to prevent rapid sinking of the crystals `as they are lifted by each blade of the spiral, as each blade rise's it lifts a mass of crystals to the discharge opening and some of them are carried out by the outtlowing liquor. This discharge is perfectly automatic without the aid of any special mechanism.

By the above means the crystals are being constantly dropped through a saturated solution which is just ready to deposit a small portion of the dissolved salt since it is being constantly cooled. This is deposited on the crystals which have already been formed instead of forming nuclei and causing the production of a great many fine crystals. It is a rather common experience in operating batch crystallizers that crystals do not commence to form gradually but the liquid becomes slightly super-cooled and suddenly a great `number of extremely tine crystals form. Such batches are generally decidedly different in appearance from normal batches.

I claim as my invention:

1. In an apparatus for crystallizing liquids, the combination of an elongated chamber, an inlet adjacent one end of the chamber whereby a heated liquid may be introduced into said chamber, an outlet for the liquid adjacent the top opposite end of the chamber whereby to maintain a level of liquid therein, a water jacket therefor adapted to have cooling water run therethrough whereby the. liquid within the chamber may be cooled, an impeller in said chamber actuable to cause the liquid to be impelled from theinlet toward the outlet.

2. In a crystallizer, the combination of a tank, means for introducing heated crystalloidal solution into said tank at one end thereof, a liquid discharge arranged substantially at the top opposite end of said tank for overflow discharge whereby to maintain said tank substantially full, means for cooling said liquid in its passage toward said discharge whereby to cause said liquid to form crystals, and means for lifting said crystals and dropping them through said liquid to assist in their growth.

In a crystalliz'er, the combination of a tank, means for introducing heated crystalloidal solution into said tank at one en.. thereof, a liquid discharge arranged substantially at the top opposite end of said tank for overflow discharge whereby to maintain said tank subsantially full, means for cooling said liquid in its passage toward said discharge whereby to cause said liquid to form crystals, and means for lifting said Crystals and dropping them through said liquid to assist in their growth, and for lifting' such crystals to said discharge whereby they may be Carried away with the outflowing liquid.

4. A crystallizer comprising a tank having an inlet and an outlet arranged to permit the lflow ofheated crystalloidal solution through siaid tank and to maintain a level of liquid therein, means for progressively cooling said solution during its flow whereby to cause the saturation of said solution and the formation of crystals, and means for lifting said crystals and dropping them through the liquid to assist in their formation, said means serving to advance said crystals through said tank and to lift and present them to the outlet for discharge therefrom with the outtlowing liquid.

GEORGE T. WALKER.

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